Manufactured by Airbus-Cisco years earlier, the Field Circus is a hick backwater, isolated from the mainstream of human culture, its systems complexity limited by mass: The destination lies nearly three light-years from Earth, and even with high acceleration and relativistic cruise speeds, the one-kilogram starwisp and its hundred-kilogram light sail will take the best part of seven years to get there. Sending a human-sized probe is beyond even the vast energy budget of the new orbital states in Jupiter system – near-lightspeed travel is horrifically expensive. Rather than a big, self-propelled ship with canned primates for passengers, as previous generations had envisaged, the starship is a Coke-can-sized slab of nanocomputers, running a neural simulation of the uploaded brain states of some tens of humans at merely normal speed.

The basic idea for a starwisp was proposed by Robert L. Forward in 1985. The device would use beam-powered propulsion; a microwave antenna would provided motive power for the sail. Once a suitable speed was reached, the probe could simply cruise to its destination.

It is noteworthy that the force produced is proportional only to the power density, and is independent of
the wavelength. Two practical choices for photon-pushed sails have been proposed: light-pushed sails
[Tsander 1924, Forward 1984, and others], and microwave-pushed sails [Forward 1985]. The microwavepushed sail (“Starwisp”) has advantages, however, it has several disadvantages. Probably the worst of these
disadvantages is the difficulty of scale, which is an unavoidable consequence of the larger wavelength of
microwaves compared to light: The 20 gram, 1-km diameter “Starwisp” probe proposed by Forward
requires a focusing lens of 50,000 km diameter-- a structure four times the diameter of the Earth!
Constructing such a lens is clearly a significant engineering project. The “Starwisp” proposal also assumes
that, to achieve low resistance, the aluminum mesh could be kept at 40°K.
(Advanced Solar- and Laser-pushed
Lightsail Concepts [1999 pdf])